Hi people, I'm new to this so here goes.

I have a Kenmore model 970-563122 side by side fridge.
I have a defrost problem. the freezer part frosts up at the back and then the crisper drawers in the fridge freeze up. I unplug and let the frost melt and then plug back in and it works for about 1 month and then the same thing. I installed one of those adaptive control boards about 2 weeks ago and the problem reappeared.
Now I wonder if it could be a thermostat or heater or temp sensor or whatever. Any help would be appreciated. The service man told me the adaptive part would work and 150 dollars for that advice was steep. He would have charged me another 150 to install it.
Thanks people